Industrial textiles comprising two layers of slit and profiled film are known. For example, WO 2011/069259 to Manninen discloses industrial textiles made from at least one layer of selectively slit and profiled polymeric film which are embossed to impart surface contouring and other properties similar to those resulting from various weave designs for woven fabrics. The film is pressed by application of heat and pressure using a chosen mold pattern so as to selectively and permanently deform portions out of plane; a slitting process is used to create apertures at the deformations to allow the passage of fluids such as air and water through the fabric. The length of the individual slits is equal to the length of the aperture formed in the film. The document also discloses that a two layer fabric can be provided in which a first layer of a suitably slit and embossed film is mated with a second similarly imprinted sheet so that the outer surfaces of the deformations formed by the embossing processes face one another. The two layers must be secured together, for example by welding, such that the upper protrusion surfaces of a first film layer are joined to the land areas of a similarly slit and profiled second film layer to create the assembled film structure.
It is known from CA 2,779,969 to Manninen to provide industrial fabrics for conveying in an industrial process which are formed from two layers of profiled and aperture film, where at least some of the protrusions on the film surface are provided with a first end integral with a contiguous land area and an opposing second end having either a detached free end or a weakened end portion arranged to be detachable from a contiguous land area in response to strain. The film provides flexibility to allow controlled relative movement of the layers to minimize the effects of internal strain.
It is further known from CA 2,779,131 to Manninen to provide a nonwoven film fabric comprising two planar polymeric films which are thermoformed according to a desired embossing pattern. The embossments are shaped such that either at least two end walls are provided with a shell-like configuration, or the side walls are materially reinforced due to the chosen slitting pattern. The size and location of the slits may be adjusted as required so as to impart a desired permeability. Nonwoven fabrics assembled from two like interengaged layers exhibit improved resistance to compressive loading in comparison to similar prior art fabrics, allowing them to maintain a void volume between the film layers and thus the chosen permeability.
U.S. Pat. No. 4,541,895 to Albert discloses a nonwoven laminated multilayer construction of unoriented polymer material, with laser drilled drainage apertures.
US 2007/0134467 to Sayers discloses a structure in which a series of film layers are laminated together and perforated to provide through openings. Perforations are cut in at least one of the film layers after the layer is secured to another layer or layers having pre-cut perforations. The size of the holes and depth of cut is varied by adjusting the laser.
US 2011/0250355 to Allum et al. discloses a method for producing a topographic pattern on a continuous longitudinal polymer fabric strip, the pattern being applied to an area of the continuous strip to be imprinted by means of an application device and the application device moving in relation to the strip in a direction which is parallel to the transverse orientation.
From WO 2005/019531 to Fitzpatrick it is known to provide a grooved and vented industrial process belt including a porous membrane which has a porous polymer coating, a permeable polymer film or an assembly of short fibers or multifilaments. The porous polymer coating can be produced by laser drilling, removal of a soluble component, mechanical punching or by applying a resin as a reticulated or nonreticulated foam.
It is known from WO 2008/145420 to Bez et al. to provide a papermaking fabric comprising a plurality of films of polymer material which are laminated on one another, wherein the films each have a plurality of perforations which extend through their thickness to provide drainage channels. The perforations may be formed by removal of a filler from the polymer of which the films are comprised.
US 2010/0236740 to Mourad et al. discloses a nonwoven industrial belt comprised of at least one film layer which has been laser drilled to form shaped through openings to enhance topography of a sheet product conveyed thereon.
From WO 2008/112612 to Levine et al. it is known to provide a suction tape for use as a tobacco conveyor belt that is formed from a continuous polymeric film containing a polymer chosen to maximize the wear resistance and minimize toxicity of any polymer contaminating the tobacco. The tape is permeable and perforated according to a desired distribution by embossing mechanically, ultrasonically, or through a laser removal technique.
WO 2012/028601 to Eberhardt et al. discloses a perforated film fabric formed from a single layer or sheet of film. The lateral edges are not perforated, while the central area of the film fabric includes a plurality of pores which form passages between the two opposing surfaces of the belt.
WO 2012/123439 to Straub et al. discloses a papermaking fabric including a first and second layer each of which is formed by one or more film-shaped tapes which adjoin one another and are arranged next to one another in the CD. The tapes are arranged such that their lateral and longitudinal edges in a first layer are offset relative to those in a second layer. The tapes in one layer are bonded by one of various means to those in the other layer.
While industrial textiles made in accordance with the teachings of the above prior art may be satisfactory in certain applications, in each case, the component film layers are not self-locking or interlockable in a manner which allows them to be permanently or semi-permanently joined together, and must be joined together in a separate bonding process in order to form the completed structure, by aligning each film layer relative to the other and bonding, which process is time consuming and may introduce inaccuracies into the resulting structure.
It would thus be highly desirable to provide a patterned and apertured film structure formed from at least two film layers, each of which was interlockable or autojoinable with the other during a single assembly process. It would be further desirable if the interlocking means provided an interconnection which was sufficiently robust such that the resulting structure was self-retaining and did not require an additional bonding step such that the two film layers would be retained in their joined configuration, but allowing for minor movements to accommodate and minimize the effects of internal strain. It would also be desirable if the interlocking means substantially prevented or eliminated any opportunity for misalignment of the two film layers to be joined. It would further be desirable if, when the film structure is intended for use as an industrial textile, a seaming component could be incorporated into the assembly. The present invention addresses this need, by providing film structures which are self-locking and are assembled from two similarly profiled film layers each of which includes protrusions and apertures which interact to provide an integrated structure having features somewhat similar to those of a woven textile, such as an internal void volume, permeability and diagonal apertures through the assembled structure which allow for passage of fluids through the assembly.